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Pipe vs Tube

srimes

srimes

NAXJA Forum User
Location
Cabot, AR
Found this interesting report on the interweb:

http://www.atarmor.com/finalreport.pdf

"The slight differences in manufacturing processes caused mild discrepancies between the mechanical properties of both materials, but they are both comparable in terms of strength and toughness."

Sounds to me like the advantage of HREW is a thinner wall. What do y'all think? ("Pipe is for poop", I know :rolleyes:)
 
Someone did a test on this over on pirate. I think they found the pipe to be stronger than HREW and a decent 88% of the strength of equivalent tube.
 
DeftwillP said:
Someone did a test on this over on pirate. I think they found the pipe to be stronger than HREW and a decent 88% of the strength of equivalent tube.
Click to expand...
From what I remember from that test, they were doing a "crush" test with t press and they were using different thickness pipes/tube.

Also, when are the cages in our sport ever put into similar circumstances as a press gradually putting 20 tons of pressure onto the tube? I want to see the test done again with the same thickness of steel and 2k lbs dropped on them from 1 foot.
 
i heard they did a test on this over on pirate. I think they found the pipe to be stronger than HREW and a decent 88% of the strength of equivalent tube.
 
crazyjim said:
No sir, it becomes the laughing stock of real fabricators ;)

Really though, pipe isn't held to NEARLY the same tolerances tube is, chemically or during manufacturing. It's brittle, uneven, and generally unreliable.
Click to expand...

Did you read the report? Granted, it is a very small sample, so maybe quality control on pipe isn't very good. But look at the test results. :rtm:

They both start as steel sheet. Do you think pipe starts from "less flat" sheet? So why would wall thickness vary more? We're comparing it to hrew, not dom here. Maybe the metallurgy varies more too, but this test doesn't find that.

In his test the 2 tube sample varied much more in thickness than the 2 pipe samples (.26mm vs .01 mm). The pipe was a little harder, but yield was almost the same, ultimate was higher on the pipe, the pipe had a little higher strain-to-failure, was more ductle, and higher fracture toughness. :lecture:

With these numbers from these samples, the tube material doesn't seem to be any better than the pipe, does it? No, I'm not a mechanical engineer (imaginary, actually), but if someone here is please correct me.

Granted, maybe pipe does tend to vary more. Anyone have testing to show it?
 
What is the BASIC difference between PIPE and TUBE. Pipe is cold formed and tube is hot formed.

Cold forming work hardens the materials and aligns grain (or something like that) to greatly strengthen steel. Work hardening continues in use until something cracks due to fatigue.

Hot forming allows forming a tube without starting to work harden the material. This leaves it more pliable.

Do your guys just use straight pieces of pipe without bending them? If you want to be able to bend the pipe/tube before you use it, you need something that hasn't already been work hardened. And when you weld it, you will stress relieve it anyway and lose the extra strength of the work hardened pipe.
 
srimes said:
Did you read the report? Granted, it is a very small sample, so maybe quality control on pipe isn't very good. But look at the test results. :rtm:

They both start as steel sheet. Do you think pipe starts from "less flat" sheet? So why would wall thickness vary more? We're comparing it to hrew, not dom here. Maybe the metallurgy varies more too, but this test doesn't find that.

In his test the 2 tube sample varied much more in thickness than the 2 pipe samples (.26mm vs .01 mm). The pipe was a little harder, but yield was almost the same, ultimate was higher on the pipe, the pipe had a little higher strain-to-failure, was more ductle, and higher fracture toughness. :lecture:

With these numbers from these samples, the tube material doesn't seem to be any better than the pipe, does it? No, I'm not a mechanical engineer (imaginary, actually), but if someone here is please correct me.

Granted, maybe pipe does tend to vary more. Anyone have testing to show it?
Click to expand...


Yes, I did read it. And I still think most of it is complete BS. I would NEVER build anything structural out of pipe. On the same token I wouldn't build anything out of HREW. CREW on the other hand yes, as well as DOM.

Wall thickness will always vary with Tube OR Pipe. The difference is Pipe is measured to inside diameter, unlike tube which is outside diameter. This gives tube a very uniform exterior.


winterbeater said:
What is the BASIC difference between PIPE and TUBE. Pipe is cold formed and tube is hot formed.

Cold forming work hardens the materials and aligns grain (or something like that) to greatly strengthen steel. Work hardening continues in use until something cracks due to fatigue.

Hot forming allows forming a tube without starting to work harden the material. This leaves it more pliable.

Do your guys just use straight pieces of pipe without bending them? If you want to be able to bend the pipe/tube before you use it, you need something that hasn't already been work hardened. And when you weld it, you will stress relieve it anyway and lose the extra strength of the work hardened pipe.
Click to expand...



You couldn't be more wrong. Not sure whose ass you pulled that information from but stop spewing bullshit when it comes to safety items.

http://www.xxxoffroad.com/index.php...-name-dom-erw-hrew&catid=31:general&Itemid=46


Electric Resistance Welded (ERW) Tube
ERW is the most economical and readily available type of mechanical tuning. It is produced by taking a flat bar of steel and rolling it into a tube shape (picture rolling up a newspaper - but without any overlap) and then welding the seam - by, you guessed it - electric resistance - hence the name. Electric resistance welding is somewhat like a long, continuous spot weld. It's often computer controlled and extremely consistent. ERW is normally SAE 1010 (for wall thickness < 16 ga) or SAE 1020. ERW tube comes in 2 flavours:

Hot Rolled ERW (HREW)
HREW is rolled into a tube at elevated temperatures, usually way above room temperature. This produces a tubing that is more malleable and therefore easier to form but that is also not as strong, is supplied covered with scale, and not as uniform in dimension as cold rolled. It is also quite a bit cheaper than cold rolled.

Cold Rolled ERW (CREW)
CREW is manufactured by a process in which a steel bar is rolled into a tube and the seam welded, usually at room temperature. Compared to hot rolled, CREW is stronger - (greater yield strength) - because of the improvement in the crystal lattice structure from improved grain size, shape, and orientation imparted by being worked at cold (room) temperatures), straighter, has a much smoother and more uniform surface finish, and is made to much tighter, more consistent dimensions. It is the best economical choice for tube work, and because of the better surface finish and tighter dimensional tolerances it is much nicer to work with than HREW.

Drawn Over Mandrel (DOM)
Strong and well-finished DOM is an electric resistance welded tube tested for soundness of weld and drawn through a die and over a mandrel. This process imparts significantly improved mechanical properties to the tube, due to the cold working process. It is considered a high quality tube, and is normally constructed from SAE 1020 or 1026 steel. Note that, technically DOM refers to the process by which the tube is finished after having started as an ERW tube. Technically, DOM is not a type of steel tube, but rather a process. As so often happen though - in common use the term has become accepted to mean a specific type of tubing rather than a process. In this case, when people say "DOM" they normally mean an ERW tube drawn over a mandrel at (close to) room temperature and made from SAE 1020 steel. It is normally drawn to O.D. and I.D. dimensions. Here is what the Steel Tube Institute of North America has to say about DOM:
Click to expand...
 
Quoting a long article does not make you right. The article says that "cold working and cold forming.........generally reduces stress". Anyone who knows anything about working metal knows that this is not true. Not EVER true. Try using some common sense instead of worrying about who pulled what from whose ass.
 
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